T-W

The event that causes a virus to act. The trigger can set off the virus on a certain date (Friday the 13th, or April 15) or when certain conditions have been met (such as when the hard disk is 80 percent full).

A type of program that pretends to be a useful (usually well-known) program while it really does something else, such as erase files from your computer. Unlike computer viruses, Trojan horses can't duplicate themselves.

Operating system originally developed at Bell Laboratories in the early 1970s. Unix is one of the most popular operating systems in the world, developed primarily for larger computers, such as mainframes and minicomputers, although a free version of Unix, called Linux, has been gaining popularity on personal computers. See Linux.

A type of antivirus program that claims to protect files from virus infection.

A program that hides in your computer's memory and watches for signs of a virus infection.

A program sold by Microsoft that lets you visually design a program and then write BASIC commands to make the program work.

A special version of Visual Basic, often abbreviated as VBA, designed for creating programs within Microsoft applications such as Word, Excel, PowerPoint, and Access.

A program that can dial a range of phone numbers, searching for a modem on the other line. Can also be used to repetitively dial a single phone number, thereby harassing the recipient. Also called a demon dialer.

Slang term for pirated software, usually games. Also called appz.

To restart a computer without turning it off and on again. Most computers have a restart or reset button, or you can press CTRL-ALT-DEL.

A tiny, invisible graphic file used to track a person's activities on the Internet.

Modifying or replacing web pages with new ones that often display profanity, pornography, or political messages. See Hacktivism.

To intercept a user's request to view one website and display a different Web site with the intent to deceive.

Term used to describe a hacker who uses his or her skill for constructive purposes, such as hunting down pedophiles or guarding against malicious (black hat) hackers. See Black hat hacker.

A type of program that copies itself from computer to computer. Unlike a virus, a worm doesn't infect a file or disk but simply reproduces itself.

A program that can combine two separate programs into a single file, most often used to combine a Trojan horse installation program with an installation program for a legitimate program. Also called a binder or joiner.